4 EAMBLES OP A NATURALIST. 



cules*, of every form and name, which multiply by 

 self-division (fissiparous reproduction), so that it may 

 literally be said that the son is half of his parent, and 

 the grandson the quarter of his grandsire. 



Such studies are highly attractive even when con- 

 sidered on the simple grounds of curiosity: this, 

 however, is not their only claim upon our attention, 

 for they possess another and a far greater source of 

 interest. In the higher forms of animal life, the size 

 and opacity of the organs do not allow of our study- 

 ins: the mechanism of their actions and functions 

 in the living state ; in their case we must content 

 ourselves with the mere study of their anatomy. 

 In the lower animals, on the other hand, we are 

 enabled to trace the operations of nature at the very 

 moment of their accomplishment : thus, for instance, 

 in the animalcule we can follow the alimentary 

 molecule from the very moment in which it is 

 swallowed until it is rejected by the animal, after 

 having yielded up all its nutritious matter. The 

 changes which this molecule undergoes in its passage 

 through the animalcule, and the successive action of 

 the animal organs and fluids, are all displayed before 



■with which the entire surface of the body is covered. These 

 ■worms, whose anatomical structure presents many singularities, 

 have been carefully studied by many naturalists, amongst whom 

 may be especially mentioned Von Baer, Duges and De Quatrefages, 

 CErsted, Von Siebold and Dalyell. 



* We have shown (see Appendix, Note I.) that the Infusoria must 

 be provisionally regarded as forming a class of the subdivision of 

 the globular Zoophytes. Amongst the principal writers on this 

 group of animals we may especially mention O. F. Miiller, Ehren- 

 berg, and Dujardin. 



